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ORIGINAL RESEARCH Table of Contents   
Year : 2009  |  Volume : 20  |  Issue : 1  |  Page : 17-20
Comparative evaluation of the surface tension and the pH of calcium hydroxide mixed with five different vehicles:An in vitro study


1 Department of Conservative Dentistry and Endodontics, Ragas Dental College, Chennai, India
2 Department of Conservative Dentistry and Endodontics, Sri Venkateswara Dental College, Chennai, India

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Date of Submission13-Apr-2008
Date of Decision16-Jul-2008
Date of Acceptance06-Sep-2008
 

   Abstract 

Aim: The aim of this study was to evaluate the surface tension and pH of five different vehicles that are used as potential agents to mix calcium hydroxide in root canal treatments and to compare them with the final surface tension and pH of calcium hydroxide mixed with these vehicles.
Materials and Methods: The study was carried out in two phases. In Phase I, the surface tension and pH of five vehicles (distilled water, saline, anesthetic solution, chlorhexidine, and glycerin) were evaluated using a Du Nuoy Tensiometer and a pH Meter. In Phase II, a predetermined amount of calcium hydroxide was mixed with the individual vehicles and the surface tension and pH was determined. In each group, seven samples were evaluated.
Results: Among the individual vehicles, chlorhexidine had the least surface tension values (39.8+1.1 dynes/cm). Among the various calcium hydroxide mixtures, calcium hydroxide with chlorhexidine showed the least surface tension values (36.4+1.1 dynes/cm). All the vehicles showed an acidic pH ranging from 5 to 6.5. There was a significant increase in the pH values with the addition of calcium hydroxide to the respective vehicles. The calcium hydroxide mixtures had an alkaline pH ranging from 9 to 11.5; the highest pH was observed for calcium hydroxide mixed with distilled water and saline (11.5+0.2).
Conclusion: The surface tension and pH of the vehicles directly influenced the surface tension and pH of the calcium hydroxide mixtures. Chlorhexidine was found to be a better vehicle for calcium hydroxide when used as an intracanal medicament.

Keywords: Calcium hydroxide, intracanal medicament, pH, surface tension, vehicles

How to cite this article:
Poorni S, Miglani R, Srinivasan M R, Indira R. Comparative evaluation of the surface tension and the pH of calcium hydroxide mixed with five different vehicles:An in vitro study. Indian J Dent Res 2009;20:17-20

How to cite this URL:
Poorni S, Miglani R, Srinivasan M R, Indira R. Comparative evaluation of the surface tension and the pH of calcium hydroxide mixed with five different vehicles:An in vitro study. Indian J Dent Res [serial online] 2009 [cited 2019 Oct 17];20:17-20. Available from: http://www.ijdr.in/text.asp?2009/20/1/17/49050
Calcium hydroxide, introduced by Herman in 1930, is considered to be the gold standard for intracanal medicament because of its antibacterial action, ability to induce hard tissue formation, and its tissue dissolving capability. All these actions are due to the high concentration of hydroxyl ions released by calcium hydroxide that make it alkaline. [1] Calcium hydroxide powder for intracanal dressing is used by mixing calcium hydroxide powder with different vehicles such as distilled water, normal saline, anesthetic solution, propylene glycol, camphorated monochlorophenol (CMCP), glycerin, cresatin, chlorhexidine, etc. [2],[3] The dissociation of calcium hydroxide into OH - and Ca ++ depends on the vehicle used to prepare the medicament. [4]

For calcium hydroxide medicament to act effectively as an intracanal dressing, it should have the ability to occupy all of the pulp space thereby diffusing into the areas inaccessible to instruments. The diffusion of calcium hydroxide into these areas is directly related to the surface tension of the intracanal medicament. [5]

Surface tension by definition is a force existing between the surface molecules, which cause a drop of liquid to spread or to concentrate when placed on a surface. This phenomenon depends on the values of cohesive forces (forces of attraction resulting from the forces that the liquid molecules exert between themselves) and adhesive forces (forces that the surface molecules exert on contact with those of a liquid). It has been shown that a reduction in surface tension increases the penetration capability and its flow into remote areas. It has also been established that low surface tension facilitates intimate contact to occur between the intracanal medicament and the dentinal walls. [6],[7]

The release of hydroxyl ions from calcium hydroxide is essential for the mineralization and microbial control processes. [8] These properties of calcium hydroxide can be more effective only if the surface tension of the intracanal medicament is reduced. Since calcium hydroxide medicament is prepared by using various vehicles that provide alkalizing pH, it is essential to know the surface tension and pH of individual vehicles and their combination with calcium hydroxide. To our knowledge the effect of chlorhexidine on the surface tension values of calcium hydroxide have not been evaluated extensively. Thus, we attempted to analyze the influence of five different vehicles on the surface tension and pH of calcium hydroxide paste. Hence, the aim of this study was to evaluate the surface tension and pH of five different vehicles that are used as potential agents to mix calcium hydroxide in root canal treatment and to compare them with the final surface tension and pH of calcium hydroxide mixed with these vehicles.


   Materials and Methods Top


This study was carried out in two phases. The vehicles used in this study were distilled water, normal saline (0.9% sodium chloride, Nirlife Healthcare, India), anesthetic solution (lignox 2% A, Indoco Remedies Ltd., India), chlorhexidine (hexidine 0.2%, ICPA Health Products Ltd., India), and glycerin (Indian Pharmaceuticals, India).

Phase I

The surface tension and pH of the individual vehicles were evaluated. Vehicles were divided into five groups. Group Ia - distilled water, Group Ib - saline, Group Ic - anesthetic solution, Group Id - chlorhexidine, Group Ie - glycerin. Seven samples were evaluated in each group. Each sample consisted of 50 ml of the vehicle taken in a glass beaker. Surface tension for the samples was evaluated using a Du Nuoy Tensiometer (DST9005, Nima Technology Ltd., England) and pH was evaluated using a pH meter (Digital pH tester, V.M. Tecknologies, India). Values were recorded and then tabulated.

Phase II

The surface tension and pH of calcium hydroxide (Sigma Aldrich, Germany) mixed with different vehicles were evaluated. Five groups were studied based on the vehicles used. Group IIa - distilled water + Ca(OH) 2 , Group IIb - saline + Ca(OH) 2 , Group IIc - anesthetic solution + Ca(OH) 2 , Group IId - chlorhexidine + Ca(OH) 2 , Group IIe - glycerin + Ca(OH) 2 . Seven samples were evaluated in each group.

Preparation of the Sample

In this study, samples were prepared by mixing 80 mg calcium hydroxide in 50 ml of the vehicle. Physical balance was used to measure the calcium hydroxide powder. Measured calcium hydroxide powder was added to 50 ml of the vehicle taken in a glass beaker and mixed with a vortexer for 1 minute.

Surface tension was evaluated using a Du Nuoy Tensiometer (DST9005, Nima Technology Ltd., England) and pH was evaluated using a pH meter (Digital pH tester, V.M. Tecknologies, India). The working principle of the Du Nuoy Tensiometer is based on the force required to detach a platinum wire ring from a liquid surface or from the interface between the two liquids. Distilled water was used as zero calibration. All glass equipment from the tensiometer were cleaned by immersion in the cleaning solution and the platinum ring was cleaned by flaming. The measurements were taken at room temperature. Values were recorded and then tabulated. A paired t test was used to analyze the surface tension and pH values. The confidence limit was 95%.


   Results Top


This study was performed to compare the mean surface tension and pH values of calcium hydroxide when mixed with five commonly used vehicles for calcium hydroxide. [Table 1] and [Table 2] show the mean surface tension and pH values of the vehicles and calcium hydroxide mixtures. Among the individual vehicles, chlorhexidine had the least surface tension values (39.8+ 1.1 dynes/cm) and distilled water had the highest surface tension (70.5+ 2.2). Among the various calcium hydroxide mixtures, calcium hydroxide with chlorhexidine showed the least surface tension values (36.4+ 1.1 dynes/cm) and calcium hydroxide with distilled water showed the highest surface tension values (66.5+ 1.2). All the vehicles showed an acidic pH ranging from 5 to 6.5. There was a significant increase in the pH values with the addition of calcium hydroxide to the respective vehicles. The calcium hydroxide mixtures had an alkaline pH ranging from 9 to 11.5, the highest pH observed was for calcium hydroxide mixed with distilled water and saline (11.5+ 0.2).

[Table 3] demonstrates the mean difference in the surface tension and pH values for the mixtures and the individual vehicles. A highly significant difference in the mean surface tension and pH values were found in all the mixtures when compared with their respective individual vehicles (P = 0.00).

Thus, this study demonstrated a significant decrease in the surface tension values in all groups with the addition of calcium hydroxide while there was an increase in the pH values.


   Discussion Top


Intracanal medicament should ideally be placed deeply and densely into the canal spaces by spreading the medication thoroughly. Spreading of the intracanal medicament in the irregularities of the canal and its subsequent diffusion into the dentinal tubules depends on its surface tension. Low surface tension increases liquid penetration into the inaccessible areas. Ideally, the surface tension of the calcium hydroxide mixture should be low to allow better penetration into the inaccessible areas. [7]

For preparation of calcium hydroxide samples, solubility of calcium hydroxide in water was considered as a standard measurement. Solubility of calcium hydroxide is 0.16 g in 100 ml of water. [5] For experimental purposes, calcium hydroxide was taken in solution and not in paste form.

Results of this study revealed that the various vehicles used had an influence on the surface tension of the calcium hydroxide mixtures. The values of this study also showed a significant decrease in the surface tension values with the addition of calcium hydroxide powder.

Distilled water alone had a surface tension of 70.5 dynes/cm, which decreased to 66.5 dynes/cm with the addition of calcium hydroxide powder. Distilled water alone or in combination with calcium hydroxide presented the highest surface tension. This can be attributed to the known fact that water has the highest surface tension of the known liquids.

Saline, glycerin, and anesthetic solutions had a surface tension higher than chlorhexidine, which decreased with the addition of calcium hydroxide powder.

Chlorhexidine alone had a surface tension of 39.8 dynes/cm, which decreased to 36.4 dynes/cm with the addition of calcium hydroxide. Chlorhexidine alone and in combination with calcium hydroxide presented the least surface tension values. This can be attributed to the fact that commercially available chlorhexidine formulations contain a surfactant, [9] which reduces the surface tension significantly. They do so by adsorbing the liquid-gas interface. A good surfactant has hydrophillic (polar or ionic) and hydrophobic (hydrocarbon or fluorocarbon) parts in the same molecule. Because the hydrophillic parts of the molecule do not bond to one another very well, it is easier to stretch the surface of the water. [10] Hence, the surface tension for chlorhexidine was low (39 dynes/cm). With the addition of calcium hydroxide, there was a further decrease in the surface tension (36 dynes/cm).

Selection of the mixing vehicle exacts the pH values of calcium hydroxide mixtures. [7] Different vehicles permit hydroxyl ions to release from calcium hydroxide to different degrees. [4] The therapeutic effects of calcium hydroxide depend on the dissociation of calcium and hydroxyl ions and the availability of hydroxyl ions. [1] The greater the number of hydroxyl ions, the higher the pH.

In slightly soluble substances such as calcium hydroxide, there is undissolved solute at any point in time. As long as some undissolved solute is present in contact with the saturated solution, the concentration of ions in the solution remains constant. As the hydroxyl ions are being consumed, the dissolution of calcium hydroxide will continue to maintain its equilibrium. Thus, an aqueous preparation of calcium hydroxide will continue to maintain the equilibrium. [1]

Estrela, et al. [11] reported that the action of calcium hydroxide would explain how its high pH inhibits enzyme activities that are essential to bacterial life, i.e., metabolism, growth, and cellular division. Siqueira, et al. [12] reported that the hydroxyl ions act on molecules or structures that are essential for microbial metabolism or reproduction. The release of hydroxyl ions in an aqueous environment causes damage to the bacterial cytoplasmic membrane and disrupts both the protein denaturation and DNA of bacterial cells.

The pH of calcium hydroxide in its pure form is 12.5, [13] whereas the pH of calcium hydroxide mixed with vehicles is less. This is due to the chemical reaction products occurring between the calcium hydroxide powder and the vehicles that cause a decrease in the pH. Fava, et al. [2] reported that the anesthetic solution with or without vasoconstrictors has been used as a vehicle for calcium hydroxide in many clinical situations involving periapical pathology. It is interesting to note that these solutions have an acidic pH, but when mixed with the calcium hydroxide powder, the final mixture has a high pH that is maintained over time. Jenkins, et al. [14] considered that the antimicrobial action of the chlorhexidine is due to the attachment of the cationic molecule to the negatively charged bacterial cell wall altering its permeability. Thus, a bacteriostatic effect occurs at low concentrations. At high concentrations, a bactericidal effect is observed by the precipitation or coagulation of cytoplasmatic contents. Maria, et al. [4] considered that the antimicrobial effect is believed to be dependent on alkaline pH. Ca(OH) 2 placed in the root canal elevates the pH producing an alkaline environment in areas of root resorption by diffusion of hydroxyl ions through the dentinal tubules.

The effectiveness of calcium hydroxide as an intracanal medicament is enhanced owing to an alkaline pH and decreased surface tension. Hence, selecting a vehicle for the preparation of intracanal medicament depends on its pH and surface tension. From the results of this study, considering the pH and surface tension, it can be concluded that chlorhexidine would be a better vehicle for mixing calcium hydroxide.


   Conclusion Top


Within the limitations of the study, it could be concluded that the surface tension and pH values of the vehicles directly influenced the surface tension and pH of the calcium hydroxide mixtures. Among the vehicles evaluated in this study, chlorhexidine was found to be a better vehicle for calcium hydroxide as an intracanal medicament.


   Acknowledgment Top


The authors would like to acknowledge the faculty of the Central Leather Research Institute, Chennai and the Department of Biochemistry, Ragas Dental College and Hospital for their help rendered during the various stages of this study.

 
   References Top

1.Safavi K, Nakayama TA. Influence of mixing vehicle on dissociation of calcium hydroxide in solution. J Endod 2000;26:649-51.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]
2.Fava LR, Saunders WP. Calcium hydroxide pastes: Classification and clinical indications. Int Endod J 1999;32:257-82.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]
3.Ballal V, Kundabala M, Acharya S, Ballal M. Antimicrobial action of calcium hydroxide, chlorhexidine and their combination on endodontic pathogens. Aust Dent J 2007;52:118-21.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]
4.Maria Gabriela Pacios, Maria Luisa de la Casa, Maria de los Angeles Bulacio, Maria Elena Lopez. Influence of Different vehicles on the pH of Calcium hydroxide paste. J Oral Sci 2004;46:107-11.  Back to cited text no. 4    
5.Gomes BP, Ferraz CC, Vianna ME, Rosalen PL, Zaia AA, Teixeira FB, et al . In vitro antimicrobial activity of calcium hydroxide pastes and their vehicles against selected microorganisms. Braz Dent J 2002;13:155-61.  Back to cited text no. 5  [PUBMED]  
6.Pecora JD, Guimarγes LF, Savioli R. Surface tension of several drugs used in endodontics. Braz Dent J 1991;2:123-7.  Back to cited text no. 6    
7.Ozcelik B, Ta?man F, Oπan C. A comparison of the surface tension of calcium hydroxide mixed with different vehicles. J Endod 2000;26:500-2.  Back to cited text no. 7    
8.Pecora JD, Estrela C, Silva RS. pH Analyze of Vehicles and Calcium Hydroxide Pastes. Braz Dent J 1998;3:41-7.  Back to cited text no. 8    
9.Available from: http://www.wipo.int/pctdb/en/wo.jsp?WO=1998%2F31332andIA=WO1998%2F31332andDISPLAY=DESC. [last accessed on 2008 Mar 19].  Back to cited text no. 9    
10.Available from: http://www.newton.dep.anl.gov/askasci/chem03/chem03058.htm. [last accessed on 2008 Mar 19].  Back to cited text no. 10    
11.Estrela C, Sydney GB, Bammann LL, Felippe O Jr. Mechanism of the action of calcium and hydroxyl ions of calcium hydroxide on tissue and bacteria. Braz Dent J 1995;6:85-90.  Back to cited text no. 11    
12.Siqueira Jr JF, Lopes HP. Mechanisms of antimicrobial activity of calcium hydroxide: A critical review. Int Endod J 1999;32:361-9.  Back to cited text no. 12    
13.Pecora JD, Estrela C, Neto D, Estrela CRA, Bammann LL. Effect of vehicle on antimicrobial properties of calcium hydroxide pastes. Braz Dent J 1999;10:63-72.  Back to cited text no. 13    
14.Jenkins S, Addy M, Wade W. The mechanism of action of chlorhexidine: A study of plaque growth on enamel inserts in vivo. J Clin Periodontol 1988;15:415-24.  Back to cited text no. 14  [PUBMED]  

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Correspondence Address:
S Poorni
Department of Conservative Dentistry and Endodontics, Ragas Dental College, Chennai
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.49050

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    Tables

  [Table 1], [Table 2], [Table 3]

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